How do I convert RPM to Hz?

Divide RPM by 60. For example, 3000 RPM = 3000/60 = 50 Hz. This gives the fundamental (1×) frequency. Hz means cycles per second, while RPM means revolutions per minute.

What are harmonics in vibration analysis?

Harmonics are integer multiples of the fundamental (1×) frequency. The 2× harmonic is twice the fundamental, 3× is three times, etc. Different fault types generate specific harmonic patterns — for example, misalignment often shows strong 2× components.

What does the 1× vibration frequency indicate?

The 1× frequency corresponds to one event per revolution. The most common source of 1× vibration is mass unbalance. Other 1× sources include bent shaft, eccentric rotor, and resonance excited at running speed.

Why are higher harmonics important?

Higher harmonics help diagnose specific faults: 2× often indicates misalignment or looseness, blade/vane pass frequency is the number of blades × RPM, gear mesh frequency is the number of teeth × RPM. Each harmonic pattern points to a specific root cause.

What is the difference between Hz, CPM, and orders?

Hz (Hertz) = cycles per second. CPM (Cycles Per Minute) = Hz × 60 = same value as RPM for 1× order. Orders are multiples of the shaft speed: 1× = one per revolution, 2× = two per revolution, etc. Orders are speed-independent, while Hz/CPM change with RPM.

免費工程工具 · #008

諧波頻率計算器

將 RPM 轉換為 Hz 並顯示 1× 至 20× 諧波。振動分析與機械診斷之必備工具。

RPM → Hz 1×–20× 次諧波 Hz & CPM

結果

1× 基頻

—

週期 (1× 週波)

—

角速度 ω

—

階次	頻率 (Hz)	CPM	週期 (ms)

RPM 轉 Hz 換算

以 Hz 為單位的基頻 (1× 次諧波) 等於轉速除以 60：

諧波頻率

每個諧波 (次諧波) 均為基頻的整數倍：

其中 n 為諧波次數 (1, 2, 3, …)。

角速度

振動中常見的諧波來源

階次	常見來源
1×	不平衡、軸彎曲、偏心
2×	不對心 (角度/平行)、鬆動
3×	不對心 (嚴重)、鬆動
N×	葉片/導葉通過頻率 (N = 葉片數量)
Z×	齒輪嚙合頻率 (Z = 齒數)
½×	油膜渦動、摩擦
0.43×	油膜振盪

實務範例

範例 — 3000 RPM 馬達

已知： 轉速 = 3000 RPM

1× = 3000 / 60 = 50 Hz (3000 CPM)

2× = 2 × 50 = 100 Hz (6000 CPM)

3× = 3 × 50 = 150 Hz (9000 CPM)

週期 = 1 / 50 = 20 ms

ω = 2π × 50 = 314.16 rad/s

💡 提示： 在振動分析中，諧波頻譜模式是關鍵的診斷工具。不平衡會顯示顯著的 1× 峰值，不對心會顯示強烈的 2×（有時還有 3×），而軸承缺陷會產生與軸承幾何形狀相關的非同步頻率。